New York City police detectives searched a studio apartment in Las Vegas that belonged to the suspected gunman in Monday's mass shooting at a Midtown Manhattan.

A gunman from Las Vegas shot five people, killing four, including an off-duty New York City police officer, inside a Manhattan skyscraper, before fatally shooting himself, officials confirmed Monday.

Four people, including an off-duty New York City police officer, were killed Monday when a gunman carrying a rifle opened fire inside a Midtown Manhattan office tower, authorities said.